Summary

Description

An intertidal brown seaweed, found on the high shore. It grows up to 40 cm long, without air bladders and lives for up to 4 years. The species can tolerate a high level of desiccation. Fronds have a characteristic ridge along the edge of the receptacles.

Recorded distribution in Britain and Ireland

All coasts of Britain and Ireland

Global distribution

Iceland, Norway, Denmark, Netherlands, UK, Ireland, Atlantic coast of France, Spain, Morocco, Azores, East coast of America from New Jersey to Nova Scotia and isolated reports in the Northern Pacific.

Biology information

Fucus spiralis spends up to 90 percent of the time out of the water. It can tolerate a high level of desiccation, being able to survive 70 to 80 percent water loss. Distinct varieties of Fucus spiralis have been recognised, such as Fucus spiralis forma nanus, which is a dwarf form present on exposed shores. Fucus spiralis also hybridises with Fucus vesiculosus providing considerable difficulty in identification.

Habitat Information

Fucus spiralis favours rocks with many cracks and fissures, which probably provide some protection for developing zygotes and adult plants. It can extend into estuaries up to the 10 psu isohaline. The presence or absence of suitable substrata is considered to be one of the most important factors determining the distribution of Fucus spiralis.

Larval characteristics

Life history information

Fucus spiralis is hermaphroditic. Receptacles are initiated during late January to February, gametes discharged during July and August, and the receptacles shed by November, although exact timing of reproduction depends on location and the form of the plant.
Young plants usually reach a length of 8 to 10 cm or more before they form receptacles. Reproduction usually begins before or during the second years growth. Vegetative recruitment occurs by the formation of new fronds from existing holdfasts. This form of reproduction is important in existing stands of the population, whereas recruitment by eggs is more important in disturbed areas or in areas where germlings are protected e.g. rock crevices.

This MarLIN sensitivity assessment has been superseded by the MarESA approach to sensitivity assessment. MarLIN assessments used an approach that has now been modified to reflect the most recent conservation imperatives and terminology and are due to be updated by 2016/17.

Physical pressures

Fucus spiralis is permanently attached to the substratum so would be removed upon substratum loss. The species has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

The effects of smothering would depend on the state of the tide when the factor occurred. If smothering happened when the plant was emersed, all surfaces of the plant would be buried under the sediment preventing photosynthesis. If smothering occurred while the plant was immersed some of the plant would escape burial allowing the plant continue photosynthesis. The species has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Fucus spiralis can tolerate desiccation until the water content has been reduced to 10-20% (Lüning, 1990). If water is lost beyond this critical level irreversible damage occurs. As the plant lives at the upper limit of it's physiological tolerance the plant cannot tolerate increased desiccation and the upper limit of the species distribution on the shore would become depressed. Decreased desiccation may allow the plant to grow further up the shore and may result in the species being competitively displaced by faster growing species. The species has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Fucus spiralis can tolerate an emersion period of 1-2 days. If emersion lasted for longer than this, the plant would suffer from desiccation and nutrient stress and the upper limit of the species distribution on the shore would become depressed. A reduction in the period of emersion may result in the species being competitively displaced by faster growing species and may allow Fucus spiralis to grow further up the shore. Recovery would be high because the species has been observed to rapidly recruit to cleared areas of the shore.

An increase in water flow rate may cause some of the plants to be torn off the substratum. Decreases in water flow rate are unlikely to have any effect. Fucus spiralis has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Fucus spiralis can tolerate temperatures from -0.5 to 28 °C. The species is well within it's temperature range in the UK. Decreases in temperature are unlikely to have any effect because the species extends into northern Norway where water temperatures are cooler. Increase in temperature may be beneficial because the optimum temperature for growth of the species is 15 degrees C (Lüning, 1990). However the species showed suffered some damage during the unusually hot summer of 1983 when temperatures were on average 8.3 degrees C higher than normal (Hawkins & Hartnoll, 1985).

The species would only be affected by turbidity when it is covered in water, due to a reduction in the light available for photosynthesis. However, Fucus spiralis spends up to 90 percent of it's time out of the water and can photosynthesise effectively in air, so it would not be affected significantly by a change in turbidity.

Fucus spiralis lives on sheltered to moderately exposed shores. Increases in wave exposure beyond this would result in plants and germlings being torn off the substratum or mobilisation of substratum with the plants attached. Decreases in waves exposure are unlikely to have any effect, because the species occurs in very sheltered conditions. Fucus spiralis has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Abrasion may kill germlings and damage the fronds of established seaweeds. Fucoids are intolerant of abrasion from human trampling, which has been shown to reduce the cover of seaweeds on a shore (Holt et al., 1997). Germlings are probably particularly intolerant of this factor. Fucus spiralis has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Fucus spiralis is permanently attached to the substratum and would not be able to re-establish itself if removed. The species has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Adult fucoid algae accumulate heavy metals and are generally fairly robust in the face of chemical pollution (Holt et al., 1997). However, germlings appear to be intolerant of heavy metal pollution. Copper retarded the growth rate of Fucus spiralis sporelings at concentrations greater than 5.8 µg/l and caused permanent damage in sporelings exposed to concentrations of 12.24 µg/l for 10 days (Bond et al., 1999). The species has been observed to readily recruit to cleared areas (Holt et al., 1997) so recovery rates are expected to be high.

Hydrocarbon contamination

High

High

Moderate

Low

Fucoids generally show limited intolerance to oils (Holt et al., 1997). However, Fucus spiralis disappeared from heavily oiled shores some months after the Amoco Cadiz oil spill. The species suffered less than Pelvetia canaliculata but more than fucoids further down the shore, probably due to it's position high on the shore, which means the oil can be present on the algae for a long time before being washed off (Floc'h & Diouris, 1980).

Radionuclide contamination

No information

Not relevant

No information

Not relevant

Insufficientinformation

Changes in nutrient levels

Intermediate

High

Low

Low

Decreases in nutrient concentration may decrease growth rate in Fucus spiralis. A slight increase in nutrient concentration may enhance growth rates but high concentrations of nutrients would lead to overgrowth of the plants by ephermeral green algae. However, Fucus spiralis is reported to be more common than other fucoids in the sewage polluted inner part of the Oslofjord, Norway (Fletcher, 1996). Recovery rate should be high because cleared areas of the shore are rapidly recruited by this species.

Additional information

Importance review

Policy/legislation

Status

National (GB) importance

-

Global red list (IUCN) category

-

National (GB) importance-

Global red list (IUCN) category-

Non-native

Native

-

Origin

-

Date Arrived

-

Native

-

Origin

-

Date Arrived

-

Importance information

Fucus spiralis does not support encrusting or sessile epifauna although the amphipod Hyale and the littorinids Littorina obtusata and Littorina saxatilis occur amongst fronds which provide shelter from desiccation. A range of epiphytes may also grow on the fronds.

Bibliography

Anderson, C.I.H. & Scott, G.W., 1998. The occurrence of distinct morphotypes within a population of Fucus spiralis. Journal of the Marine Biological Association of the United Kingdom, 78, 1003-1006.

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